Electrical measuring instrument.



l. W. BR O GGEFL,

ELECTRICAL MEASURING INSTiUMENT.

APPLICATION mm mmzz. 1913.

1,141,523. Patented June 1, 1915.

3 susns-sntn 1.

Fig.1.

l. W. BRUGGER.

ELECTRICAL MEASURING INSTRUMENT.

,APPUCATION FILED MAR. 22, 1913.

1 1 4 1 5 23 Patented June 1, 1915.

3 SHEETS$HEET 2.

I 25 I 8/ l r l L i I H 49% m1 V n 2 i. W. B RUGGER. ELECTRICAL MEASURING INSTRUMENT.

APPLICATION FILED mm. 22. 1913.

1,141,523. Patented June 1, 1915.

3 SHEETS-SHEET 3 Fig. l'o.

WIT "E8858:

UNITED GREECE- 1 NAB-.W. BEliGGEB; or NEWARK, NEW JERSEY.

ToJa'Zl whom; it may concern! Be it known that =1, Ivan WV; Bnocenm'a subject of the Kin dam of Norway, residing at Newark, in t e county of Essex and Stateof New Jersey,- have invented certain fic'ation.

This invention relates to electrical measuring instruments of the DArsgnval type having a coil pivotally mounted-in a magnet field with two spiralsprings to. conduct the current into and out of the coil andproviding the resistance to swinging oi said -coil.

It is understood that in order to produce an instrument of the above type of high quality, the torque, whichis produced by the magnetic lines of for ce and the' limited amount ofcurrent allowed to pass through-- E iac'rmcAL MEASURING msmnnnzmm Specification of Letters Patent.

Improvements-in Electnica-l-Measuring In istruments,;of which the following is a speciits whole circumference the coil winding, must be as great as pos sible, also the dampi'ng action' produced by the magnetic lines; and the closed frame when thelatterswings in the field must be as near, perfect as possible. A high torque enables the'use of'strong controlling springs ion whiclrtheaccuracy and durability ofthe instrument to a great ez'gtent depend, and

also. the attainment of other-desirable 'features such as high resistance or a low drop instrument or' a' temperaturecompensated millbvbltmeteror' ammeter, all features which 'are greatly appreciated by usels of instruments of the above type, as they are the basis for great accuracy and economy of operation Such torque and damping are secured by such a relation of the magnet and the movable coil to each other as that the greatest possible number of: magnetic lines nagneti conductors; tosecure n uniformscale,- with equal dlVlSlOHS or graduations; by means'of theldetail shape of isaid ..-mag-.f

supported from opposite sides by thes oppo site bridges for holding the coil; to secure canbe broughtto act on the windings to produce torque and on the coil frame to produce the damping effect by means-of the eddy currents-induced in the frame. Furthermore, it is important to utilize to the fullest extent the whole length: of the windings on the coil for producing the torque in order to make the ratio of the weight of the windings to the torque they'produce, when current is passing, a minimum. Or, in other words, since the ohmic resistance of the windings determines the amount of current fiowirig'through them, a certain potential being given, the best results are obviously obtained when every unit "length of the 'windings produces part of the total torque,

when current is passing, or in other words Patented June1,-1915;

Application filed mm 22,1918. Ser1x1Fo.-7 5$,l43.-

th'e-ratio of watts dissipated in the windingsto torque produced-should be a minimum.-

therefore; 1 I are .-to-. enable .a magnet-to be used whose thIOlHIBSS- in a direction perpendicnler' to The ob ects of the invention;

the'zpla-ne of the magnet is less zthenits width ordimensionin the plane-of the mags net; to therebyreducethemside area. of the magnet and decrease the leakage flux;-to

reduce the useless field or stray lines-of force between thepoles-of the magnet outside the co ljby means of magnetic conductors; to increase the-.efliciencyof the the magnetic lines of force a more efficient damping action on the coil due to the eddy currents generatedv inxthe closed coilframe;- to reduce the reluctance of the magnetic the increase of aree'through which-linesoi force pass from one poljto: thefothenj to thus obtain greater permanency of them age':

netic field, and increased "-cfli'ciencyifof. the magnet to further reduce this reluctance by a core mounted inside the'coil in 'the (plane .of the-magnet; and extending'in between-the 'netic conductors; to enablejthe core to be improved frame for the coil, which can be stamped and folded from sheet -meta-lorotherw isc formed, :with" improvedmeans i for; mounting pivots on the frame; to provide improved means for balancim the indicator;

tin securing'the indicator in non-rotatable reletion"to,- the' partly broken away to show the eons'tructionf more clearly; Fig. 3 is a section of theme strument on :line A-A of Fig: L; Fig

coiiby's'ub' 'te to the action-of nd. producing path between the-poles. by-

shows the coil and indicator removed; Fig. 5 is a perspective view of one of the bridges; Fig. 6 is a detail view illustrating the mounting of the core upon tlge bridges; Fig. 7 is a detail perspective of a springsupporting arm for adjusting the indicator; Fig. 8 is a perspective view\of the coil frame partly folded into final shape; Fig. 9 is a plan of the measuring instrument complete, in its case; Fig. 10 is a .view of a modified form of magnetic conductor applied to a magnet; Fig. 11 is a section of the magnet and core corresponding to Fig. 3 showing diagrammatically the path of the magnetic lines; Fig. 12 is a view of the mounting of one of the coil springs on a pivot pin of the moving coil frame, showing the same in central section at right angles to the section shown in Fig; 3 and on larger scale, and Fig. 13 is a view of the mounting for the pivot screw and tension lever on one of the bridges, showing the same in central section at right angles to the section shown in Fig. 3 and on larger scale.

In said drawings,.i indicates a magnet of the horseshoe type, although itmight be of other forms, and preferably this magnet is formed of layers or laminations 2 eachof which is in turn formed of unequal sections or plates 3 and 4, the plates of different layers breaking joints as indicated in Fig. 1. This is done to failitate assembling and enabling warpin tofbe corrected but the layers may also e made continuous. The poles of the magnet are at their adjacent faces recessed or curved concavely, in plan, preferably on thearcof a circle, as at 5, 6 in Fig. 2, and at its upper and lower sides the magnet is provided at said poles with magnetic conductors 7 8 projecting toward each other beyond the two poles, and preferably concavely curved at the middle portions oftheir adjacent edges, as at 9, 10 and having said edges acceding at both ends of the curve as at 11, 11 and 12, 12. These magnetic conductors may be located only at the poles of the magnet, as shown in Figs. 1, 2 and 3, or they may extend over the entire upper and lower surfaces of the magnet and formadditional layers or laminat-ions therefor, as shown at 13, 13, in Fig. 10, and can be made of magnet steel or soft steel according to whether the one or the other is wanted.

It will be noted that the receding end edges 11, 12, of the magnetic, conductors, are shown flush with the corresponding receding end portions of the pole faces, see Fig. "20f the drawings more especially. The effect of this construction is that the receding portions of the pole faces are widely separated so that there is only a little leakage between them, while the more closely np-.

proaching points of the magnetic conductors have no great thickness and"therefore the leakage is small. By the construction of poles and magnetic conductors described substantially the same amount of metal is provided for conducting lines cf force to be traversed by the .rnovlng coil hereinafter described whatever the angular position of said moving coil may be. In other Words, the moving coil is traversed by substantially the same number of lines of force whatever its angular position, due to the middle curved portions and outwardly diverging end portions of the pole faces and edges of the magnetic conductors which I have described herein.

On both top and bottom of the magnet, outside the magnetic conductors, are secured bridges 14, 14, which are similar to each other although oppositely arranged, of course. Each of these bridges coniprises a non-magnetic platelike body 15, of sheet metal or made as a die casting and having apertured cars 16, 16 at its opposite ends to rest upon the magnetic conductors 7, 8, and

receive bolts 17, 17 extending through said cars 16, 16 of both bridges, both the upper and lower magnetic conductors 7, 8 and the magnet 1, to secure all of said parts together. The body 15 of each bridge is cut away centrally of itself, forming an opening 18, and spanning this opening in the direction of a line connecting the ears 16, 16 is a portion 19 preferably formed as part of the plate 15 and held, by bent ends 20, 20, spaced from the body 16 in parallel relation thereto, within the opening 18, and upon a center line perpendicular to the center line through the ears 16, 16, is a pair of similar cars 21, 21, and at the ends of that outer edge of the body 15 which is toward the closed end 'of the horseshoe magnet '1, are spaced ears 22, 22 to receive screws 23, for holding the scale plate.

Through the cars 21, 21 of both upper and lower bridges extend bolts 24, 24, which also extend through a preferably disk-like core 25 thus held in proper position between the polesof the magnet. Said core is rigidly held spaced from the bridges 14, 14 by means of sleevesQG, 26 upon the bolts 24, 24 and between the bridges and core upon opposite sides thereof. Thesleeves 26, 26 may also serve to locate the magnet in assembling it.

with the unit consisting of core, coil and bridges held together by the b alt-s 24, 24, and

act also as stops for the frame in its extreme path for the. lines of force between the adja cent poles of the magnet, in order to secure the best possible results from the instrument. 115 will he understood, however, by those skilled in the art that this core could he made of nonqmigmctio material or indeed could be omitted entirely, and tho instr' r inont would still Work although in a very inferior Way. A soil 2? extends around the core 25, in a plane tramvorse thereto, so as to swing between said core and the poles and roagnotin conductors, 7, 8 oi the magnet, and is pivotally supported from the loentup 1301* tions 19, 19 of the bridges, as will he hero-- inuftor described. Said coil formed of wire Wound upon a frame which oonsii tubes one of the feotureg; of my invention. The blank for this frame, best shown in Figs. 8, 4 and 3, is prefemhly stamped out of a single piece of sheet material, and after Word bent into the desired form and proton ably soldered at the overlapping and. When so bent it provides two parallel sides 29, 30 held in spaced relation to each other by means of the ends 31, 31, so-that a reotongzw ltLI frame is rovided, around which the Wire is wound in the plane of the frame. in order to prevent the Wire of the soil from slipping laterally oil the frame, retaining flanges 33, are bent up at the edges of the parallel sides 29, 30. I also provide supporting extensions projeriing from the op posito sides of the frame and eaoh compris ing Wings 35, 36 or 37, 38 projecting from the longitudinal edges ol' both parallel sides; 29, L30 or the flanges 33, 34 thereof, said wings hung equidistant from the ends of the frame. Tho outer ends of orieh pair of Wings are prefomhly bent inward at Substantially right, angles to su wrpose one upon the other, at 3:), l0 or l1, 42, said overlapping ends being preferably apertured as at 43, or ll fortho introduction of a pivot pin 45 or 46 socirred thereon to the frame by any suitohlo means, such inner and outer nuts l7, 48 or 49, 5!), at opposite sides of the parts upon said pin and clampingithe. samo togetln' rh in order to pivotallv support the frame 29,- o sorow 51 is provided centrally in each of the bent up portions 1%), 19 of the bridges i4, 14, it being understood that said screws 51, 51 are in axial alinemont with and adapted to pivot ll y receive the ends of the pivot pins 45, 4!. of the coil. Friction may be reduced between the screws 51. and the pivot pins by use of jewels (not shown) in the ends of the screws, as is old and Well-known in the art, and v vhioh mnstruction I preferably employ. Surrounding each of tho screws 51 is a look out outside the bridgo 14. which look not has a. reduced portion for spacing the head 54; away from the bent up portion 19 of the "bridge and upon earl of the sold reduced portions 53, and insulated tlilerefrom as well as from the bridge 14, is a tension lefior 55 adapted to be swung in a plane perpendicular to the axis of the coil and. haviu one end bent inward toward. the llldfllfii} su stantially parallel to said axis, 118 at :36, and. having its other end. prov ded with it longitudinal slot '37. in order to trio tionally retain said lovers; in desired an olar position, I place on the reduced portion 53 of each lock out 52, between its; head 5% and the tension lever 55, a spring Washer 58, said Washer and tonsion lever being insulated one from the other as shown. The tension levers 55, 53, are connected with the terminals of the instrument in any suitable. and Welllmown manner, not shown.

It may here be noted that the dislvshoped core is supported in axial ulinemont with the pivot pins 45, lo of the coil frame and screws 51 pi'votally supporting the 5211116, and also at the centers of the. openings 18-, 18 of the bridges ll, l i. The frame sup porting the Wire coil 27 is cmistruoteil so that the air gap between it, the pole faces, and the mognotio conductors, the least possible permitting lio coil to swing with-- out obstruction. Similarly the (lis osha pod core 25 is shaped so no to minimize tho air space between itself and the (oil 27. without obstruoting the free swing of the latter,

Spiral springs 55-9, (3.0 coiled flirt like clock springs, ure supported upon opposite sides of the l'i'amv 28 by lmB-xing their inner ends secured fixedly to insulated terminals 32 upon the pivot pins 45, 46, sold terminals being clamped in fix-9d relation to the core frame by the nut; 4-8 and 50. Tim inner ends of said springs have the extremities; of the oomieoteil thereto, and the outer coil wire ends of mid springs 51), fill are woured. 21 by ooldoi'ing, tillill to tho bent down portion .36 of the adjacent tonhion lever 1'35. These springs 59, (ll) thus lie in pianos suilistnntiully perpendicular to the axial lino upon which the coil 27 swings and their tension is adjusted so as to normally hold said coil in its zero position when. no current pausing ihrougfh the ('Oll. Not only do the coil Springs 9, (il thus hold the roll. loot zit tho name time they constitute. (.(lllllcfitlhlifs for leading a current from tho terminals: of the inutr unont through the coil. Thus by connelstiijig' the iormirmis of the insirummit. with :1. source of olortro motive force. the urn-rent will flow thrmigh the windings of the coil, and said coil will he deflected according to the amount of current, nll ordingr a measure Ofit. 1

Upon the pivotal pin 45 at the upper side f the coil I place a pointer or indicator (ll, projecting toward the nosed end of the ins-19 not 1 and adapted to indinato upon a scale Gil the movements of the coil. Thin pointer is arranged upon the pin 45 betwoen the folded wing ends 39, 40 of the frame and the terminal 32 to which is fastened the inner end of the coiled spring 59, and is widened at opposite sides of the pin as at 63, (see Fig. 4), and provided with flanges 64- 6d bent down over the edges of said folded liaps 39, 40 to prevent twisting of the pointer with respect to the coil-frame. The rear end or short arm 65 of the pointer 61 has a trans verse counter balance ()6 which can be reduced at its rear edge 67 or either of its lateral end edges 38, (l8, as by clipping or filing, to secure a balanced condition of the indicator or pointer (ll, moving coil 27 and frame 28 pivoted between the screws 51, 51. lh'e other arm 39 of said pointer overlies the scale (32, and said scale in my improved construction made with equal graduations, or division lines equidistant from one an other, which conduces to the greatest ease and accuracy in producing said markings mechanically by means of a printing device. To enable such equal graduations the action of the lines of force on the coil when current is passint through the latter must be of constant magnitude regardless of thadiflcrcnt angular positions of the coil so that the deflection is directly in proportion to the cur rent. In other words, the torque produced by the lines of force between the poles of the magnet which are cut by the coil must not differ in angular position of the coil. and l accomplish this by shaping the curves 9, 10 of the magnetic conductors, either semi-- elliptical as shown, with the major axis of the ellipse extending from the center of one pole of the magnet to the center of the other or otherwise as found desirable. By this construction the inevitable leakage at the corners of the magnet poles, weakening the active field at these points, is compensated for by the magnetic conductors projecting farther over the coil and core at the corners than at the middle of the poles and thereby strengthening the field where the magnetic leakage tends to weaken it. A uniform action between field and the current through the coil is thus insured for all positions of the coil. It can readily beseen that also other scale characteristics can be obtained with my construction as tor instance a scale with divisions narrower at the ends and wider in the center and vice versa. Also an increment or decrement of scale division from one end of the scale to the other can be obtained by properly sloping the magnetic conductors. \Vhen a uniform scale is desired in instruments as heretofore constructed the length of scale is limited on account of the leakage at the corners, but with my construction a maximum scale deflection can he obtained as the. leahage atthe corners is compensated for by the aforesaid shape of the magnetic conductors. In all instruments of this type, because of wear, misuse, or climatic conditions, the pointer may not be in exact registration with the zero of the scale when the coil is free from any flow of current. In order to correct this error, I have provided in the casing 70, a. pivot or adjusting pin '71, having at its outer or exposed end means whereby it may be turned, such as the slot 72 adapted to receive a screw driver or the like. The opposite or inner end of this pin 71 carries-a disk from which projects toward the 'back of the instrument an ecceutrically positioned pin 74, engaging within the slot 57 of the tension lever 55. Turning of the adjusting pin 71 will therefore result in angular swinging of the lever to which is secured one end of the coiled spring 59 and as the other end of said spring 59 is connected with the coil frame and pointer, the pointer may be brought to register with the zero of the scale by the user of the instrument without having to remove the casing.

It should be noted that an important feature of my invention is the construction of bridges 14 to which the core 25 and coil 27 upon its frame may be attached entirely independent of the magnet, so tha assembling of the instrument is simplified and cheapened. Similarly it will be noted that the simplicity of parts and their adaptation to be made by inexpensive processes, and yet at the same time so to be accurate, durable and interchangeable, are market, advant ges of this instrument; and as the section and laminations of the magnet 1 may be magnetized separately just as well as after as sembly, the process of manufacture of the magnet is cheapened and facilitated.

Various changes may be made, by those skilled in the art, from the (let ail construction which I have positively shown and described, and I do not wish therefore, to be understood as limiting myself thereto. For instance, instead of forming the magnet and magnetic conductors of the identical pieces 1 have. shown, they can be builtup in any other suitable way. r

Having thus described the inventiomwhat I claim is i 1. In an electrical measuring instrument a magnet with adjacent poles, a movirg between said poles, a core with in said moving coil, and magnetic conductors project ing toward each other from the facing sides of the, poles above and below said moving coil and having their adjacent edges con. cavely curved so that the mcvmg coil is traversed by substantially the, same number of lines ot force in difierent angular positions.

2. In an electrical measuring instrument, a magnet with adjacent poles, a moving coil between said poles, and magnetic conductors projecting toward each other from the facing sides of the oles above and below said moving coil and aving their adjacent edges mamas concavely curved at their middle portions and inclined outwardly apart at their end portions.

'3. In an electrical measuring instrument, a magnet with adjacent; poles having facing sidesacurved in the plane of the magnet a moving coil between said poles,' a core within said moving coil, and magnetic "conductors projecting toward-each other from said'facing sides of thepoles'abovevand below said moving coil and having their edges concavely curved so that the movimr coil is traversed by substantially the same number oflines of force in different angular positions. Y I

4. In an electrical measuring nstrument,

' a magnet yvith adjacent polesfhaving facing sides curved in the plane of the magnet, a moving coil between said poles, and mag; netic conductors projecting toward each other from said facing sides of the poles above andbelow said moving coil and having their edges concavely curved at their middle portions and inclined outwardly apart at their end portions. g

. 5. Inan electrical measuring instrument,

-a magnet with-adjacent poles having facing sides concavely curved-atstheir middle portions and incl ned outwardly apart at their end portions, axmoving coil between said curved portions of the facing sides of the poles, and magnetic conductors projecting toward each other fromysaid facing sides of the poles above and; below saidmoving coil and having "their edges concavely curved at *thoir middle portions, and inclined outmagnetic conductors projecting wardly apart attheir end portions in sub-,

stantially the planes of the said inclined end portions of the pole faces.

6. In an electrical'measuring instrument of the character described, the combination with a magnet havingfacing poles, a core between said poles an'da'm-oving coil rotatably arrangedibetween said poles and core with a substantially uniform air-gap, of from the on 7 posite sides of the magnet beyond the faces of said poles and overlying said coil, the amount of such pro ection varying at differcnt points along-the fi'ice of' the poles so as .to regulate the .action of the lines of-force positions of and over-15in; said coil, the an'ioiint of such projection being least at the middle of the pole faces and increasing toward both ends other fat the top and bottom of the magnet, means securing said bridges'in fixed: relation to each other independently of the magnet,

so as to secure a constant action of the field on the coil regardless of theangular position of the latter. Y V

r 8. In an electrical measuring instrument, the combination with a magnet, of opposite bridges extending from one pole to'the other at the top and bottom of the magnet, a'mo u ing coil mounted in said bridges entirely be r tween the-same, a core within said] 'oving coil, means for attaching said-cereal; opposite .points to said bridges, and means for securingsaid bridges tosaid magnets 9. In'an electrical measuring instrument,

the'combination with a magnet, of 015130 site bridges extending from one'pole to the a moving coil mounted in saidrbridges entirely between the same, and means for so curing said bridges to the "magnet, 10. In an electrical measuring instrument,

'the combination with a magnet, of opposite bridges extending from one pole to the other at the top and bottpinlof the magnet, a inoving coil mounted entirely between said bridges, a core within said moving coil, means midway between thepoles foratt'achv ing said core t6 said bridges, and meansfOr securing said bridges'to the magnet.

11. In an electrical measuring instrument,

the combination with a magnet, of' opposite bridges extending from one pole'to the otherat the top andrbottom of themagn'e't, a mov ing coil entirely between said bridges, a core within said moving coil, bolts-extending 100 through said bridges and 'corejsubstantially in aline through the axial line of the' m'oving coil and midway betiive'en the 'poles,'a nd sleeves on said boltsbetween said core and bridges holding the core in 'spaced relation 105 to the bridges.

12. In an electrical measuring instrument, the combination with a magnetofa frame comprising upper and lower parallel portions, of both said parallel portions at substan tially right angles thereto each Emir of wings having its ends, bent toward each other and over-lapping, a coil wound on said frame,.

means upon said overlapping wing endsforr 115 pivotally mounting the frame and bridges on the magnet adapted to receive said mounting means. i

13. In au electrical measuringinstrument,

the combination with a magnet, of a frame 120 comprising opposite upper and lower portions, wings iirojecting from the opposite edges of both said portions away from the frame, and each pair having ts ends bent toward each 1' ihcr and over-lapping, a coil 125 wound on said frame between theeai's of each pair, pivot pins mounted U1 said-overlapping ends of the wings and projecting i wings projecting fromopposite edges oppositely away from the frame in aline-- same, means on said bridgelike portions of the frame for pivotally mounting the same, and means on the magnet for receiving said mounting means.

15. In an electrical measuring instrument, the combination with a magnet, of a moving coil frame having a coil wound thereon, said frame having at its upper and lower sides supports which project over the winding at a distance therefrom, means on said supports for pivotally mounting the frame, and bridges for receiving said pivotal mounting means and connecting the moving coil to the magnet.

16. In an electrical measuring instrument 7 of the character described, the combination with a magnet having facing poles providing slots withbottoms curved in the plane of the magnet, and a moving coilarranged between said poles in said slots.

17. In an electrical measuring instrument, the combination with a magnet, of opposite bridges extending from one pole to'the other at the top and bottom of the magnet, means securing said bridges in fixed relation to each other, a moving coil mounted-in said bridges between the same, a pointer carried by said moving coil, a scale plate mounted on one of said bridges, and means for securing said bridges to the magnet, whereby the moving coil, pointer and scale plate canbv detaching the bridges from the magnet be removed without disturbing their relation to one another.

18. In an electrical measuring instrument, the combination with a magnet, of opposite bridges extending from one pole to the other at the top and bottom of the magnet, means securing said bridges in fixed relation to each other, a moving coil mounted insaid bridges between the same, a pointer carried by said moving coil, and means; for securing said bridges to the magnet, whereby the moving coil and pointer can by detaching the bridges from the magnet be removed without disturbing their rel ition to said bridges.

19. In an electrical measuring instrument, the combination with a magnet, of oppbsite bridges extending from one pole to the other at the top and bottom of the magnet,'a core between said bridges, means securing said bridges in fixed relation to said core, a moving coil mounted entirely between said bridges and inclosing said core, and means for securing said bridges to the magnet.

20. In an electrical measuring instrument, the combination with a magnet, of opposite bridges extending from one pole to the other at the top'and bottom of the magnet, a moving coil between said bridges having a projecting pivot pin, a screw in one of said bridges for said pivot pin, a headed lock-nut on said screw for locking the same, a tension lever pivoted'on the shank of said lock-nut, a spring secured at one end to said tension lever and at the other endto'said pivot pin, and a spring washer on the shank of said lock-nut adapted to press resiliently against the tension lever when said lock-nut .is seated rigidly against the bridge.

21. In an electrical measuring instrument, the combination with a magnethaving adjaeent poles, a. core between said poles, bridges mounted upon opposite sides of said core in spaced relation thereto, a moving coil mounted entirely between said bridges and inclosing said core, and means for securing said bridges to the magnet.

IVAR W. BRGGGER. Witnesses Howann I. KING, Minonno E. Bnocns. 

